Well, it looks like the D3 beta is going to go up sometime this summer, according to a blue post on the Blizz D3 forums. Make sure your battle.net accounts are updated to show you want to participate in betas! Although I think, honestly, the first round will most likely be for last year's Blizzcon beta cards and a few select invitees from D2 mp or some such.
Knowing how Blizz operates, if they go for the latest announced date, September 30, 2011, and take a 6 month beta period, that would put D3 as a Q1-2012 game at the earliest.
Source:
http://forums.battle.net/thread.html...o=1&sid=3000#9